Hard floor cleaning these days is done by first vacuuming the floor, followed by mopping it. Vacuuming removes the coarse dirt, while mopping removes the stains. From the state of the art many appliances, especially targeting the professional cleaning sector, are known that claim to vacuum and mop in one go. Appliances for the professional cleaning sector are usually specialized for big areas and perfectly flat floors. They rely on hard brushes and suction power to get water and dirt from the floor. Appliances for home use often use a combination of a hard brush and a double-squeegee nozzle. Like the appliances for the professional sector these products use the brush to remove stains and the squeegee in combination with an under-pressure to lift the dirt from the floor.
Said squeegee elements are usually realized by a flexible rubber lip that is attached to the bottom of the cleaning device and merely glides over the surface to be cleaned, thereby pushing or wiping dirt particles and liquid across or off the surface to be cleaned. An under-pressure, usually generated by a vacuum aggregate, is used to ingest the collected dirt particles and liquid.
In current single rotating wet brush floor cleaning devices it is an issue that dirt particles are not picked up by the vacuum air flow but get launched across the floor. This leads to a disposal of the dirt across the floor but not to the actually intended cleaning of the floor. The problem is that by using rotating brushes the dirt particles are scattered within the housing in an unpredictable way. Especially at high rotation speeds of the brush the trajectory of the dirt particles bouncing forth and back between the brush and the interior of the housing is most of the time completely random and therefore unpredictable. In some floor cleaning devices of the prior art this problem is tried to be solved with large vacuum aggregates that provide a high suction power. However, it is evident that such large vacuum aggregates are not only cost-intensive, but also consume a lot of energy. Apart from that large vacuum aggregates are quite noisy.
Experiments of the applicant have shown that even if powerful vacuum aggregates are used, the problem of unintentionally dispersing the dirt with the brush over the floor may not be completely overcome. In most known cleaning devices according to the prior art the dirt particles are scattered within the interior of the nozzle in such an uncontrolled manner that not all dirt particles are directly guided into the nozzle outlet.
In case of cleaning devices with a single rotating brush this often results in the fact that the dirt particles that have been picked up by the brush will make a further turn with the brush, which throws them back onto the floor again. Especially when the exhaust is not able to catch (suck) the dirt particles away from the brush and into the nozzle outlet, the brush may take the dirt particles back to the floor again. As a result, the dirt particles may be shut out of the nozzle again and get dispersed over the floor. It is evident that this does not lead to a satisfactory cleaning result.
An exemplary device that uses a brush to disperse the dust in combination with an air flow created by a vacuum aggregate to lift the dispersed dust is known from WO 2005/074779 A1. This device includes a vacuum aggregate to create an under-pressure with a suction chamber that is delimited at its front and rear side by delimiting ends, such as runners. The rotary brush is arranged inside the suction chamber. The brush is used to sweep the floor and disperse the dust, which is then ingested by the vacuum source. The two delimiting elements that are proposed according to this solution are designed to be vertically mobile, so that they can be lifted depending on a forward or backward movement of the nozzle. These delimiting elements have the function to stabilize the under-pressure with the suction chamber in order to receive a constant suction flow (a constant under-pressure) within the suction chamber independent of the movement direction of the nozzle.
However, the device proposed in WO 2005/074779 A1 includes several disadvantages. First of all, the construction including the two delimiting elements is rather complicated and interference-prone. Secondly, the brush which is used in this vacuum cleaner is an agitator (also denoted as adjutator) with stiff brush hairs to agitate the carpet. An assembly including such an agitator requires a high suction power in order to receive a satisfactory cleaning result especially on hard floors. Therefore, large vacuum aggregates need to be used which again result in a high consumer price of the device. Apart from that, this device does also not solve the problem that the dirt particles are scattered in an uncontrollable manner and may get launched back to the floor. Similar as explained above it seems problematic to guide the dirt particles in a more or less controlled manner away from the brush and into the nozzle outlet.
EP 0 265 205 A2 discloses a floor cleaner in which driven rollers are integrally mounted with a pair of rotating cleaning bodies on the respective opposite end portions thereof, each of the rotating cleaning bodies being provided with a plurality of blades made of an elastic material on the outer circumference thereof. The wheels comprise pairs of main wheels disposed at forward and rear portions of the casing. The floor cleaner further comprises auxiliary wheels, each of which is located at an intermediate position defined between the respective driven rollers, and each of which is positioned somewhat lower than the respective main wheels.
WO 84/04663 discloses a machine for cleaning of preferably hard surfaces which machine has two against each other rotating brushes. The brushes throw through a gap between them dirt particles to a container. Between the brushes and the container runs a transport channel for the dirt particles and which channel is widening upwards. Means for supply of liquid detergent has permeable devices which forward liquid detergent to the brushes because of the rotation of the brushes.
JP 2003033305 discloses a sucking instrument for floors, which is capable of improving a cleaning function along walls without spoiling the function that the sucking instrument for floor originally has. The sucking instrument comprises a sucking instrument body, a front wall of which is formed with a bumper having a revolving brush provided near the bumper. The bumper is provided with a finny part consisting of an elastic body hanging down toward the floor surface to be cleaned, and the revolving brush is placed on a location where its revolution locus contacts with or is close to the finny part.